Improving agronomic traits in crop plants is beneficial to farmers. Several factors crop yield. Abiotic stress is the primary cause of crop loss worldwide, causing average yield losses of more than 50% for major crops. Among the various abiotic stresses, drought is a major factor that limits crop productivity worldwide. Exposure of plants to a water-limiting environment during various developmental stages appears to activate various physiological and developmental changes. Molecular mechanisms of abiotic stress responses and the genetic regulatory networks of drought stress tolerance have been studied.
Natural responses to abiotic stress vary among plant species and among varieties and cultivars within a plant species. Certain species, varieties or cultivars are more tolerant to abiotic stress such as drought than others. Transgenic approaches including overexpression and downregulation are evaluated for engineering drought tolerance in crop plants. Nitrogen utilization efficiency also affects crop yield, especially where the application of nitrogen fertilizer is limited.